This application claims the benefits of Korean Patent Application Nos. 2003-51116 and 2004-26246, filed on Jul. 24, 2003, and Apr. 16, 2004, respectively, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.
1. Field of the Invention
Methods consistent with the present invention relate to manufacturing a hybrid micro-lens and an array of the hybrid micro-lenses using a machining process and either a photolithographic process or a nano-imprinting technique, for example.
2. Description of the Related Art
Examples of a conventional method of manufacturing a micro-lens array include manufacturing a single micro-lens using a machining process, manufacturing a micro-lens array using a photolithography process using a photoresist, and the like.
FIG. 1 is a schematic diagram for illustrating a conventional method of manufacturing a single micro-lens using a machining process. Referring to FIG. 1, to form a single micro-lens, an upper mold 11 and a lower mold 13 are first processed in the shape of a surface of the single micro-lens. A ball (BL)- or gob (G)-shaped lens is inserted into the space between the upper and lower molds 11 and 13 and compressed at a high temperature, thereby forming the single micro-lens. A lens used in a machining process is usually made of glass. A plastic lens is manufactured by injection molding using a precise mold manufactured by a machining process. Such a machining process can achieve precise surface processing. However, the machining process has a limit in processing ultra-small lenses and forming a lens array. Hence, the machining process is used for optical information storage media and some optical communication lenses, which require a high numerical aperture.
FIGS. 2A through 2E are cross-sectional views illustrating a conventional method of manufacturing a micro-lens array using photolithography. First, as shown in FIG. 2A, a substrate 21 is coated with photoresist 23. As shown in FIG. 2B, a mask M is positioned over the photoresist 23, which is exposed to ultraviolet rays. Thereafter, exposed portions of the photoresist 23 are developed and etched, thereby forming a photoresist pattern 23a shown in FIG. 2C. When heat is applied to the photoresist pattern 23a and causes reflow, the photoresist pattern 23a is transformed into a photosensitive lens 23b having a spherical shape as shown in FIG. 2D. Thereafter, the refractive index of the photosensitive lens 23b is adjusted using an ion exchanging technique as shown in FIG. 2E.
The conventional method of FIGS. 2A through 2E has difficulty in obtaining a high sag necessary for a high numerical aperture and performing aspherical curved surface processing required for aberration correction. Also, the conventional method of FIGS. 2A through 2E has difficulty in manufacturing a large aperture lens with a diameter of 500 μm or greater.